The invention relates in general to communications, and more specifically to a method and system for communicating between transceivers using electromagnetically coupled signals.
Standard telephone wire connections between homes and telephone central offices are configured in binder groups with ten to fifty twisted pair wires per binder group. Binder groups are combined to form multi-pair cables that can have from ten to several thousand twisted pairs. These multi-pair cables have a metallic electrical sheathing and plastic covering that shield the twisted pairs from most noise and other disturbances that exist outside of the binder group in the air or underground. As a result, the twisted pair binder group is a transmission environment that can be significantly impacted by noise resulting from signals that are transmitted on one twisted pair leaking, or xe2x80x9ccrosstalkingxe2x80x9d, into another twisted pair in the same binder group via electromagnetic energy coupling. The unwanted electromagnetic energy that couples into a twisted pair from signals transmitted on other pairs in the same binder group is called crosstalk noise, or simply xe2x80x9ccrosstalkxe2x80x9d. In most cases, this crosstalk is one of the limiting factors for the performance of all the transmission systems that are contained in a particular binder group. When crosstalk is the primary factor, the transmission environment is called a crosstalk-limited environment. One of the most problematic types of crosstalk for communicating data over telephone wires is near-end crosstalk, which is crosstalk that results from transmitters that are xe2x80x9cnearxe2x80x9d the receiver, i.e., at the same end of the wire. For example, near-end crosstalk for a receiver in a home (customer premise, CP) originates from other neighboring homes"" transmitters. This crosstalk is typically the most severe type because in this case the transmitter is closest to the receiver and therefore the magnitude of the crosstalk can be large.
One technique for decreasing the levels of near-end crosstalk in the telephone binder group transmission environment is by maintaining frequency separation between the receiving signal and the near-end crosstalking signal. In general, techniques or processes that are intended to decrease the levels of crosstalk in multi-pair metallic loop cables are known as xe2x80x9cspectrum managementxe2x80x9d plans. The American National Standards Institute (ANSI) is currently drafting an American Standard on Spectrum Management called xe2x80x9cSpectrum Management for Loop Transmission Systemsxe2x80x9d. This standard will, among other things, set rules on which frequency bands transceivers should use depending on whether they are located at the CP or the central office (CO). By implementing a spectrum management plan that dictates the frequency bands for transmission from the CO to the CP (downstream transmission) and separate frequency bands for transmission from the CP to the CO (upstream direction), one can significantly decrease the near-end crosstalk in the binder group.
Telephone companies intend to establish spectrum management plans based on the ANSI standard for their loop plant for this reason. However, even though such companies hope to enforce the rules of such a plan on new transceivers deployed in their network, little can be done about older xe2x80x9clegacyxe2x80x9d systems that may not follow these rules.
Furthermore, the spectrum compatibility problem is more complicated because in some homes people use their in-home telephone wiring for other transmission systems. One example of an in-home wiring transmission system is a home computer networking system that is used to connect multiple computer devices in people""s homes. This transmission system, also known as home phone networking (HPN), does not follow the spectrum management rules that the telephone companies want to use in their network. As a result, HPN signals that xe2x80x9cleakxe2x80x9d from homes onto the telephone network become a severe near-end crosstalk source for many telephone company-deployed services. This problem of spectrum pollution from signals that do not follow the spectrum management rules is serious and affects the availability of high-speed data access to homes and businesses. Thus, there remains a need for a system and method that can reduce the crosstalk interference encountered by transceivers communicating on wires in a binder group.
In one aspect, the invention features a method for use by a transceiver to communicate over a wire in a group of wires. In the method, communications are received over a first wire and transmits a communication signal over the first wire. The communication signal transmitted over the first wire electromagnetically couples to a second wire to produce an electromagnetically coupled signal on the second wire. The electromagnetically coupled signal conveys a message that induces a response from a second transceiver connected to the second wire.
The conveyed message directs the second transceiver to alter an operation of the second transceiver. More specifically, one embodiment of the method detects interference on the communications received over the first wire and the transmission of the communication signal occurs in response to detecting the interference. The transmission of the communication signal occurs if the detected interference exceeds a predetermined threshold. In a further embodiment, the detected interference is crosstalk.
In another aspect, the invention features a method for communicating between a first and second transceiver that are connected to different wires in a group of wires. The first and second transceivers are not connected to each other by any wire in the group of wires. One embodiment of the method transmits signals by a first transceiver over a first wire. The first transceiver receives a communication signal over the first wire. The communication signal is transmitted from a second transceiver over a second wire and is electromagnetically coupled to the first wire from the second wire. The method further includes performing an action in response to a message conveyed by the electromagnetically coupled communication signal.
In one embodiment, the performed action is an adjustment to a transmission parameter. The adjustment changes a power level used to transmit signals over the first wire. In another embodiment, the adjustment changes a frequency band used to transmit signals over the first wire. In yet another embodiment, the adjustment changes time increments used to transmit signals over the first wire.
In a further embodiment, the method includes receiving a second electromagnetically coupled signal over the first wire in response to the adjustment to a transmission parameter. The adjustment of the transmission parameter is stopped in response to the second electromagnetically coupled signal.